Potentiometer constructions



April 1959 M. E. BOURNS ET AL POTENTIOMETER CONSTRUCTIONS Filed May 3,1956 United States Patent 2,881,296 POTENTIOMETER CONSTRUCTIONSRiverside, and Edward D. OBrian, said OBrian assignor to Bourns Lab-Marlan E. Bourns,

Anaheim, Calif.; oratories, Inc.

This invention relates to new and improved potentiometer constructions.More specifically it relates to otentiometers including readout means sothat the position of a wiper within a potentiometer may be determinedthrough the use minimum of difficulty.

The terms miniature and sub-miniature are frequently mentioned in theelectrical industry today because there is an ever increasing demand forelectrical components and assemblies which are extremely small and lightin weight. A great deal of work has gone into developing different typesof so-called miniature and subminiature devices for a variety ofpurposes. In spite of this work there are, at present, no known small,compact units manufactured which combine a potentiometer with a readoutmember so that the relative adjustment or position of the wiper of thepotentiometer can be readily determined by simple visual inspection.

A broad object of this specification is to provide a small, compactlight-weight combined potentiometer and readout construction as brieflyindicated in the preceding sentence. A further general object of theinvention is to provide electrical instruments of this category whichcan be easily manufactured using established techniques, which areexceedingly reliable in use, and which are capable of withstanding agreat deal of physical abuse.

Another object of the invention is to provide various means foractuating the readout means utilized as well as for simultaneouslyadjusting the potentiometer in accordance with an electrical signal.Thus, the instruments of this invention are extremely well adapted foruse in various control applications where an analog quantity representedby an electrical current is used to adjust a potentiometer for anydesired control purpose. The amount of such adjustment can, with thedevices of this invention, be determined in a digital form by simplevisual inspection of the readout means employed.

Other objects and advantages of the invention will apof such readoutmeans with a pear to those skilled in the art to which thisspecification is addressed from a detailed examination of the remainderof this description, including the appended claims and the accompanyingdrawing, in which:

Fig. 1 is an isometric view of a potentiometer construction of thisinvention;

Fig. 2 is a cross sectional view in which certain parts are shown inelevation, taken at line 22 of Fig. 1;

Fig. 3 is a cross sectional view taken at line 3-3 of Fig. 2;

Fig. 4 is a cross sectional view taken at line 4-4 of Fig. 2; and

Fig. 5 is an isometric view showing the construction of a readout ringor wheel.

It is to be understood that the accompanying drawing is not to beconsidered as limiting the scope of this invention inasmuch as a numberof differently appearing constructions can be readily created by skilledmechanics in the field to which this invention pertains by utilizing thefeatures herein explained. Obviously various sizes, shapes, andarrangements of parts may be altered while retaining the mode ofoperation and construction involved with this invention.

As an aid to understanding the new potentiometer constructions of thisinvention it may be stated by way of an explanatory summary that each ofthese constructions involves a resistance element; a wiper positionedadjacent to the resistance element so as to be movable along it; meansfor causing said wiper to assume different positions along the length ofthe resistance element; and readout means operatively attached to saidmeans for causing said wiper to assume different positions. Theinventive concept back of the present application is more fully definedor summarized in detail by the appended claims.

The exact nature of potentiometer constructions of the present inventioncan be more fully explained by direct reference to Figs. 1 through 4 ofthe accompanying drawings. Here there is shown a device 10 of thepresent invention which includes a cylindrical metal housing 12, theends of which are closed by non-conductive generally circular plates 14and 16 formed out of a phenolic or other equivalent composition. Aroundthe periphery of each of these plates there is provided a flange 18adapted to bear against the housing 12 so as to form a substantiallysealed unit when these plates are secured to one another through the useof three shafts 20. The ends of these shafts'20 project through openings22 in the plates 14 and 16 and are threaded so that nuts 24 can beutilized to secure these plates and the housing 12 together.

Mounted upon the plate 16 which, if desired, may be considered a rearplate is a non-conductive ring 26, around the periphery of which thereis located a curved, continuous groove 28 which forms the inner race fora ball hearing, as will be described in more detail presently.Positioned upon the ring 26 is a small reversible electric motor 30which has a shaft 32 extending from the opposite end thereof. Screws 34are employed to attach the ring 26 and the motor 30 to the plate 16.Other screws 34 are employed together with small cylindrical spacers 36to position a small cylindrical speed multiplying device 38 of anydesired internal construction upon the motor 30 so that this device 38is axially aligned with the motor 30. The shaft 32 serves to connect themotor 30 and this device 38; it also serves to carry a small gear 40which is employed as will be more fully explained later. A non-rounddriven shaft 42 extends from the device 38 along the axis of this deviceon the side opposite the motor 30 so as to fit within a correspondinglyshaped socket 44 in a larger round shaft 46. The shaft 46 is rotatablysupported within a cylindrical opening 48 in the plate 14, and carries alarge drive gear- 50.

This drive gear 50 is designed so as to coact with an internal ring gear52 formed within the interior of a first readout ring or wheel 54.Within the device 10 are four of these readout rings or Wheels ofsubstantially identical construction except for certain minor details aswill be explained later. For convenience of explanation these readoutrings or wheels are designated as 54, 54', 54", and 54" respectively; aswill be more fully apparent these wheels are used to indicate successivenumbers, such as, for example, the numbers in a decimal fraction. Atleast one of the wheels are required with the invention as a readoutmeans, and any desired number of these rings or wheels can be employed.All four of these readout rings or wheels are formed as indicated inFig. 5 of the drawing so as to each include a centrally located internalflange 56. On one side of each of these flanges there is formed acontinuous internal ring gear 52 as indicated in the precedingdiscussion. On the other side of each of these flanges 56 there isformed a segmental internal ring gear 58 which, in the form of theinvention illustr'steaeitma'sroi 36 of a cirele around the interior ofeach" of these readout ring s'orwheels54f All of the read out rings orwheels 54 are preferably formed of a nontlu emate a su h as. s g gg e, nlis Q I Po i y. v 1011s M an. Numerals to 9a're'paint'edor otherwiseapplie on the exterior of each .of thesering's or wheels 5450 as to beequally spaced in o'rderfth'at he position of these wheels 54 maybevisually dete" "60' formed in a'line along the of transparent wi'dd wallof the housing 1 z.

The readout rings or'i'wlieels a're all supported with v respect to oneanother a'gainst undesiredmovement ment, and the centers of these spools62 normally, bear against the flanges 56. Itlis considered obviousthatthe various shafts 20 are spaced frorn one another a sufiicient amountso as toprevent shifting oi the readout rings or wheels 54in planestransverseto the axis of the housmg Within the device 7 n 5 eteaeri di lm ve th retra t w ned through a series 16 th I ll i title 0 .wh lsf5 ione another in accordance with -therotation of the preced- 7 insreadout. s n at wear -1 u fsfi se r-@09 5 6 rotatably mounted on a shaftsupported within openings (not shown) in the plates ld and ldf Eachofthe ea SPOQIS 6. isib m dw t e d 7 ha ns e enera shape of gears so Iby a segmental ring gear on orient the readout wheels the nt nu u ting,se .1 2 v wheel is operated so as H to turn this next adjacent ring orwheel. This mechanism of eorrelating the motion of a series of wheels inaccordance with a predeterrnined that when one of these ends is engagedthe next a ja e readou mathematical relationship enables these Wheelstobe used in designating the'digits in a nuniber Geneva cross or otherindexing movements can be substituted for the specific gear typeconnection betwelen the various readout wheels 54 so long as snch meansare locatedgenerally Q Q taiu mp et uni .I

within these wheels so v such other means are substituted care must betaken that these means do not nterfere with the other operative parts ofthe device 10.

One of these other parts is eyliridrical non;conduc tive support 72formed ot ephenolic resin or similar eompo-.

sition so as to have grooves 74 similar to the groove 28 formed on theinside thereof in such 'amanner as to hold small ball bearings 76 inorder to rotatably mount this support'72 on the ring 26' and'the deviee38, Preferably the groove 28' and the 'groove 74 imrnediately adjacentthereto are formed as illustrated so that the ballbearings around thering 26 serve to prevent shifting of the support 72 in'a direction alongits axis. Small plugs 78 can be threaded within holes 80 in the support72 for introducing the ball bearings 76 into either of the channelscarrying these i s-j 4 Around the periphery of the support 72 there islocated within the preferred embodiment of the device 10 a IO-turnhelical'resistance elerrient 82. This element 82 in the form of theinvention illustrated includes a corn tinuous "non-conductive, base 84around which is wound resistance wire 86; other types ofresistanceelements can be, employed. For mechanical stability it is preferred tolocate the resistance element 82 so that at least half of its depth issecured within a helical groove. 88 in the sup port 72 by means ofaconventionaladhesive or the like.

A helical, slot-like groove,90 having the same pitch as.

the resistance element 82is formed adjacent to this resistance elementwithin the exterior of the non-conductive support 72.

With this construction a small metallic contact member 92 having anextension 94 formed thereon is mounted upon a non-conductive block 96 sothat this extension fits within the slot-like groove causing the blockto slide along a shaft 98 secured between the plates 14 and 16 fromwithinropenings (not shown) in each. The contact member 92 also has acurved resilient extension 100 designed to engage the resistance element82 and another extension designed to engage the shaft 98 so that thisshaft may serve as an electrical return.

The support 72 is rotated during the operation of the device 10 throughthe gear 40 coacting with another gear 104 held upon an idler shaft 106positioned so as to extend between the motor 30 and the device 38. Thegear 104 coacts with an internal ring gear 108 formed on a flange .ofaring 110 secured to the interior of the support 72'as by .means ofscrews (not shown) or like equivalents. Electrical connection is made.to the ends of the resistance element 82 by meansof slip rings 112mounted on the ends of the support 72 so as to beelectrically connectedas by means of short wires (not shown) to the endsof this resistanceelement. One of these slip rings 112 is engaged by a brush 114 mountedupon the plate 16 so as to be connected directly to one of a series ofterminals 116. The other of the slip rings 112 is designed to be engagedby means of another brush 114 (Fig. 3) mounted upon anon-conductivehollow brace 118 carried by the plates 14 and 16 A wire. 120 leadingfrom the brush 114 engagingthis other slip. ring to another of theterminals 116 may be conveniently passed through, the brace 118.

Further, as desired, other slip -rings 115 or contact members may belocated within the interiors of the readout rings, or wheels. Such otherslip. rings or contact members can be interconnected in any desiredpattern so that when engaged by brushes such as the brushes 114 variouselectrical devicesmay be actuatedin various sequential or other manners.Thus, conductors 115 having the general shape of slip rings having gapsformed therein on the interior of the readoutvwheel 54" can be used soas to cause either the motor 30' to stop rotation or to cause this motorto reverse its direction of rotation. The terminals 116 employed may beof any known category and vmay be arranged in various configurationswith respect to .one another for convenient mountingin sockets or thelike. 7 v

It is considered that the operation of the device 10 is essentially,obvious from the aforegoingdescription of the construction of thisdevice. When the motor 30 is caused to be operated the support 72 isrotated and simultaneously the contact member 92 moves along theresistance element 82 disposed upon this support. Also, as the motor 30is, operated the speed multiplying device 38, which, if desired, may betermed gearmeans, is actuated so as toturn the gear 50, turning thefirst readout ring or wheel 54. Once during every revolution of thismember a gear spool'66 causes the second readout ring or wheel 54' tomove a fraction of a turn. When the second readout ring or wheels 54 hasbeen moved so as tofinish a complete ,turn the third readout .ring orwheel 54 is then turned a fraction of a. turn andso on until the fourthring or wheel 54". is turned onecomplete revolution corresponding in atime interval to the period required ,for the contact member 92 to movecompletely along the resistance element 82. It will be realized fromtheaforegoing description that the device 10 is essentially a verycompactefiective gear trains are attached to shafts projecting from eachend of it to operate the readout wheels and the support 72. It ispossible to replace the motor 30 with various other structures forcausing rotation of a known category. Further, it is possible in somedevices utilizing a series of concentrically mounted members as hereindefined to incorporate an amplifier within certain of the membersutilized. If desired the entire device may be mounted directly upon asmall amplification unit used to operate the motor 30. Since this device10 is, as formed, entirely reversible it is very advantageous for manyapplications. Obviously a five or other number of turn resistanceelement can be used instead of the specific resistance ele-- ment shown.With any construction of this invention care must be taken that thereadout means and the potentiometer wiper are operatively interconnectedso that they are both actuated simultaneously in accordance with adesired mathematical pattern or interrelationship.

Because of the fact that a large number of modifications such as areindicated above may be made in the structure shown without departingfrom the essential features of this invention, the appended claims areto be afforded wide scope, and are not to be considered as being limitedby the specific construction disclosed.

We claim:

1. An electrical instrument of the class described which includes: aresistance element; a wiper mounted adjacent to said resistance elementso as to be capable of being moved along said resistance element; meansfor moving said wiper along said resistance element; a series of readoutwheels rotatably mounted around said resistance element and said wiper;means for rotating a readout wheel of said series as said wiper is movedalong said resistance element; and means for rotating the other of saidreadout wheels in said series in accordance with the rotation of saidreadout wheel.

2. An electrical instrument of the class described which includes: asupport; a resistance element mounted on said support; means for movingsaid support; a wiper mounted adjacent to said resistance element so asto move along said resistance element as said support is moved, saidwiper continuously engaging said resistance element as said support ismoved; a series of readout wheels rotatably mounted around saidresistance element and said wiper; means for rotating a readout wheel ofsaid series as said wiper is moved along said resistance element; andmeans for rotating the other of said readout wheels in said series inaccordance with the rotation of said readout wheel.

3. An electrical instrument of the class described which includes: ahousing; a resistance element rotatably mounted within said housing; acontact member mounted within said housing so as to engage saidresistance element as said resistance element is rotated; at least onereadout wheel rotatably mounted in said housing around said resistanceelement and said contact member; and means interconnecting saidresistance element and said readout wheel so as to simultaneously rotatesaid resistance element and said readout wheel so that the position ofsaid contact member with respect to said resistance element can bedetermined by the position of said readout wheel.

4. An electrical instrument of the class described which includes: ahousing; a cylindrical support rotatably mounted within said housing; ahelical resistance element mounted upon said support; a contact membermovably mounted within said housing adjacent said resistance element,said contact member engaging said resistance element; means for movingsaid contact member along said resistance element as said support isrotated; movable readout means mounted within said housing around saidresistance element and said contact member; and means connecting saidreadout means and said support so as to move said readout means inaccordance with the rotation of said support whereby the position ofsaid contact member with respect to said resistance element can bedetermined by the position of said readout wheel.

5. A potentiometer construction which includes: a housing; a resistanceelement rotatably mounted within said housing; a contact member mountedwithin said housing so as to engage said resistance element as saidresistance element is rotated; a series of readout wheels rotatablymounted within said housing; a reversible electric motor mounted withinsaid housing; gear means connecting said resistance element to saidelectric motor so that as said motor is operated said resistance elementrotated; gear means connecting the first of said series of readoutwheels to said electric motor so that as said motor is operated saidfirst readout wheel is rotated and means for rotating said readoutwheels of said series in accordance with the rotation of said firstreadout wheel.

6. A potentiometer construction which includes: a housing; a cylindricalsupport rotatably mounted within said housing; a helical resistanceelement mounted upon said support; a contact member movably mountedwithin said housing adjacent said resistance element, said contactmember engaging said resistance element; means for moving said contactmember along said resistance element as said support is rotated; aseries of readout wheels rotatably mounted within said housing aroundsaid support and said contact member; means for rotating the firstreadout wheel in accordance with the rotation of said support; means forrotating the remainder of said readout wheels of said seriesperiodically in accordance with the rotation of said first readoutwheel; and terminal means electrically connected to the ends of saidresistance element and said contact member.

7. A potentiometer construction which includes: a housing; a hollowcylindrical support rotatably mounted within said housing; a resistanceelement mounted on said support so as to extend around said support; acon tact member mounted within said housing so as to engage saidresistance element as said support is rotated; a series of readoutwheels rotatably mounted within said housing so as to be positionedaround said support and said contact member; an electric motorpositioned within said support; and gear means connecting said motor tosaid readout wheels and said support so that said readout wheels arerotated to positions indicating the position of said contact member withrespect to said resistance element when said support is rotated throughthe operation of said motor.

8. A device of the class described which includes: a housing; a hollow,cylindrical support rotatably mounted within said housing; a helicalresistance element mounted upon said support; a contact member movablymounted within said housing adjacent to said resistance element, saidcontact member engaging said resistance element; means for moving saidcontact member along said resistance element as said support is rotated;a series of readout wheels rotatably mounted within said housing aroundsaid support and said contact member; an electric motor positionedwithin said support; gear means operated by said electric motor forrotating said support; means operated by said electric motor forrotating the first of said series of readout wheels in accordance withthe rotation of said support; means for rotating the remainder of saidreadout wheels of said series periodically in accordance with therotation of said first readout wheel; and terminal means electricallyconnected to the ends of said resistance element and to said contactmember.

Harrison Oct. 13, 1931 George Jan. 30, 1951

